Magnetic dirt collector



Aug. l2, 1969 C, A STUMPF 3,460,294

MAGNETIC DIRT COLLECTOR Filed sept. 2&3, 1967 avsnetsneet 1 7o 15 .I nli w 18 482%. um [www Y; 68

l m 7B CHARLES A. STUMPF A TTOR/ YE YS Aug. l2, i969 A, STUMPF 3,460,294

MAGNETIC DIRT COLLECTOR Filed Sept. 28, 1967 2 ShBGtS-Sheet 2 FIG-6 c@itABSTRACT OF THE DSCLOSURE A tubular housing having the inner surfacesthereof magnetized for depositing the magnetizable dirt particles whichare produced when a grinding wheel machines a piece of metal. Thehousing can be easily adjusted to position its opening to receive thestream or dirt, and batlles or projections can be used to increase thearea on which the particles can be deposited, to vary the pattern of themagnetic lines of force, and to create turbulence to insure that theparticles are deposited in one of the surfaces in the housing. When anelectromagnet is utilized, a phase reversing switch is provided tofacilitate removal of the metal particles from the housing.

Background of the invention It is necessary to collect and dispose ofthe dirt produced when a grinding wheel is utilized to smooth andmachine a piece of metal. For the purpose of this disclosure, this dirtincludes about 90% magnetizable metal particles removed from theworkpiece and about of the non-metallic materials removed from thegrinding wheel. If the dirt were not collected, it would becomeentrained in the air around the machine and be damaging to the health ofthe operator when inhaled. It would be deposited both on the workpieceand the precision machine elements of the grinding machine making itdillicult or impossible to maintain the necessary tolerances for highprecision grinding.

The prior art devices utilize vacuum systems to draw the dirt into aconduit. These vacuum systems include two types, to wit, the individualtype wherein the vacuum system is provided for each grinding machine,and the central system wherein a large vacuum pump is provided -for aplurality of grinding machines. In any case, both of them are expensiveand very noisy which decreases the efiiciency of the operators. Inaddition, the individual system is space consuming since it must belocated or mounted in close proximity to the machine. The central systemusually eiects the dirt into the atmosphere outside of the buildingcausing air pollution and decreasing the effectiveness of the airconditioning system since the air within the building containing thegrinding machines is being pumped to the outside. Moreover, the centralsystem limits the flexibility in the physical location of the machinerysince the outlets were usually provided at precise positions when thebuilding was constructed.

Summary of the invention Accordingly, the invention provides a smallhousing having the inside surfaces magnetized so that, when the dirt isthrown into this housing, the magnetic particles are deposited on themagnetized surfaces. The device is noiseless, more efficient than thevacuum system, easily cleaned, and considerably less expensive than theprior art devices. In one embodiment of the invention a vacuum system isutilized to collect the non-magnetic dirt produced during the grindingoperation.

Patented Aug. 12, 1969 Brief description of the drawings FlG. 1 is aperspective illustration of a grinding machine utilizing the magneticdirt collector in accordance with the invention;

FIG. 2 is another perspective view showing the adjustable support forthe dirt collector;

FIG. 3 is a front elevation view of the dirt collector;

FIG. 4 is a view similar to FIG. 3 with the inner liner removed;

FIG. 5 is a sectional view taken along the line 5 5 of FrG. 6;

FIG. 6 is another sectional view taken along the line 66 of FIG. 4;

FIG. 7 is a diagrammatic illustration of the electrical circuitry forthe invention;

FIG. 8 is a sectional View of a modied form of the sole plates; and

FIG. 9 is a side elevation view, partially in section, of anotherembodiment of the invention.

Detailed description of the drawings Referring to FIG. 1, theconventional grinding machine 10 is illustrated including a table 11having the horizontally reciprocating chuck 12 thereon with the metalworkpiece 14 secured in place thereon by a magnetic chuck or itsequivalent. The upstanding portion 15 of the frame 11 supports therotating shaft 16 having the grinding wheel 17 thereon which is suitablydriven at high speed in the usual manner. The protective guard 18extends around the grinding wheel 17 except the lower portion thereofwhich contacts the workpiece.

As the chuck 12 reciprocates, the workpiece 14 is moved into contactwith the grinding wheel 17 which removes a portion of the workpiece andcreates the high speed stream 19 of dirt particles consistingapproximately of magnetizable metal particles from the workpiece and 10%of the non-magnetic particles from the grinding wheel. While this is theusual content of the dirt, it is in no way intended to be a limitationon this invention. It is also possible that a grinding wheel 17 may becomposed partially or entirely of a material which is magnetizable sothat the entire content of the dirt can be collected by this invention.

The magnetic dirt collector 2i)l in accordance with the invention ismounted on the frame 11a in position to receive the stream 19 of dirt asit is propelled at high speed tangentially of the wheel 17 from the areaof contact between the wheel 17 and workpiece 14. The collector 20includes the tubular housing having the outer side walls 22, the top andbottom walls 23 and 24, and the rear wall 25. The rear portion of thesewalls is square whereas the forward potrion of the walls taper outwardlyto the edges 26.

Referring to FIG. 2, the mounting apparatus 28 for the collector 20permits adjustment of the housing in substantially any direction. Thisapparatus includes an elongated pin 3G secured to the frame 11 andadapted to receive the horizontal sleeve 31 for back and forthadjustment of the vertical rod 32 rigidly secured to the sleeve. Thevertical rod 32 has a bracket 33 received thereon adapted to be clampedonto the rod by tightening the screw 34 and looseninfI to permitvertical as well as angular adjustment. The bracket 33 also has thehorizontal sleeve 36 thereon adapted to receive the horizontal supportrod 37 extending to the bracket 38 mounted on the rear wall 25 of thehousing 20 by the screws 39.

The bracket 38 includes an intermediate member 41 pivotally secured tothe end member 42 on the support rod. 37 by the screw 43, and thisintermediate member is secured between the horizontal lingers 44 byanother screw 46. Thus, the collector housing 20 can be adjusted awayfrom the grinding wheel 17 by the sliding movement between the pin 30and sleeve 31, in a vertical direction by moving the bracket 33 on thevertical rod 32, in a horizontal direction transverse of the face of thewheel 17 by sliding the horizontal rod 37 into the sleeve 36, as well asthe minor angular adjustments effected by rotating the bracket 38 andthe housing 20' about the axis of the screws 43 and 46.

A pair of electromagnetic coil devices 50 is secured on the insidesurface 51 of each of the walls 22, 23 and 24, as shown in FIGS. 4-6,for the purpose of generating a magnetic field. Each of these devicesincludes an elongated metal core 52 in the form of a metal bar securedto the surface 51 by the machine screws 54. Surrounding the bars is acoil retainer 55 of non-magnetic material, e.g. a phenolic plastic,having the spaced arms 56 and 57 formed integrally with the center wall58 to enclose a plurality of windings 60 of electrical wire having aninsulation on the outside surface thereof. The windings are made from acontinuous wire so that when direct current is applied to the wire itflows throughout the coil and creates a magnetic field.

Each of the electromagnetic devices 50 also includes a magnetizablemetal plate 62 secured in place thereon on the inside arm 57 of the coilretainer and having a width substantially wider than the coil retainer55. The precise configuration of these plates is important since theymust be as large as possible without having contact with the adjacentplates to avoid short circuiting of the magnetic field. Thus theconfiguration of these plates is such that a space 64 is providedbetween the adjacent plates while allowing the plates to cover a maximumarea. An end barrier 65 is created within the housing by the fingers 66on each of the plates which are of different size and arranged so as toprovide a space 67 between adjacent fingers while permitting a maximumarea to be filled in by the plates. A precise configuration is shown inFIG. 4, but it is within the scope of the invention to use otherconfigurations without departing from the scope of the invention so longas there is a clearance between all areas of the adjacent plates.

An inner liner 68 of non-magnetic material, for example brass, issupported within the housing 20` and includes the side walls 70, thebottom and top walls 71 and 72, and the integral back wall 73. Each ofthese walls is in intimate contact with the magnetic plates 62 althoughthere is no shorting of the electromagnetic field because of the use ofa substantially non-magnetic material in this liner. The outer edges 75of this liner are deformed to provide a fiange which encloses the space76 between the liner 68 and the outside walls 22, 23 and 24 of thehousing with the tiange snugly engaging the outermost edges 26 of theotuside walls.

The inner liner 68 and the plates 62 are rigidly secured to the bars 52of the magnetic devices 55 by the short posts 77 (FIGS. 5 and 6) havingthe threaded studs 78 on the inner ends thereof which extend throughsuitable openings in the liner 68 and plates 62, and into threaded bores79 in the metal bars 52. Four such posts may -be mounted on each of thewalls 70, 71 and '72.

As shown in FIG. 3, the forward posts 77 on the upper and lower walls 71and 72 have the rectangular magnetic bars 80 thereon extending generallyrearwardly in the housing 20 and secured in place by the machine screws82. These bars are utilized to distribute the magnetic field and provideadditional surfaces on which the metallic particles may collect. It istherefore important that there be no contact between the bars whichwould cause shorting of the magnetic field. Moreover, these bars createa batiie effect which causes the metallic particles to swirl around inthe housing 20 until they adhere to the magnetized surfaces, thuseliminating the possibility that the high speed particles may bedefiected outwardly of the housing from the inner rear wall 73.

The operation of the magnetic dirt collector is best described inconnection with the electrical schematic shown in FIG. 7. The housing 20is first adjusted so that the center of the stream 19 of dirt particlesis received in the center thereof. Because the grinding wheel 17 remainsstationary, this pattern does not change materially as the workpiece 14passes the grinding wheel, although further adjustment may be necessaryif a large amount of metal is 'being removed from the workpiece. Thehousing 20 is mounted as close as convenient to the grinding wheel 17with the necessary clearance for reciprocation of the chuck 12. Asdisclosed above, the housing 20 can easily be adjusted up and down, backand forth, or in an angular direction as the grinder is adjusted forworkpieces of different sizes and configurations.

A source of aiternating current is supplied to the device 20 from aconventional source through the lines 86 and 87 having the on-of switch88 therein. This switch is physically located within the rear portion 90of the housing 20 (FIG. 6) and the glow light 92 is provided therein toindicate when the switch is in its on position. The alternating currentfiows to the full Wave rectifier bridge 94 of conventional design whichconverts the alternating current to direct current fiowing through thelines 96 and 97. From these lines the direct current fiows through thedouble throw-double pole switch 100 which is normally in the positionwherein the contact 101 connects the lines 96 and 102 and the Contact103 connects the lines 97 and 104. In normal use, each of theelectromagnetic coils 60 is thus connected in the lines 102 and 104 andsupplied with direct current.

The current fiowing through the coils 60 creates a magnetic field whichmagnetizes the plates 62, the posts 77, and the elongated bars 80. Sincethe plates 62 are magnetized, substantially the entire area of theinside surface of the liner 68 is subjected to magnetic field so that,as the stream 19 of dirt is thrown into the housing at high speed, itstrikes the bars 80 and is thrown against the walls 70, 71 and 72 wherethe metal particles adhere. The edges of the posts 77 and the bars 80,as well as the spaces 64 between the plates 62 create an increasedmagnetic field and thus the metal particles adhere in the area of theseareas first. However, as a substantial amount of metal particles arethrown into the housing 20, the entire area of the posts, bars, andliner are covered, with little or no particles escaping from the housing20.

When the housing 20 becomes filled with particles it can be easilyemptied in a convenient container by merely pivoting the housing 20about the vertical rod 37 to point downwardly into such container. Themain switch 88 is turned off which releases a portion of the particleswhich fall into the container. The switch 100 which is in the form of apush button switch on the housing 20 (FIG. 2) is momentarily closedcausing the contacts 101 and 103 to interconnect the lines 96 and 104,and 97 and 102, respectively, so that the direct current flows throughthe coils 60 in the direction opposite to that during normal operation.Since the metal particles will have a certain amount of residualmagnetism, the polarity reversal will repel the particles away from thesurfaces to which they are adhered thereby quickly releasing them tofall from the housing. This polarity reversal must be performed whilethe On-Oi switch 88 has been moved to its Off position, otherwise someof the particles will re-adhere to portions of the housing.

Another embodiment of the plates `62 is shown in FIG. 8 wherein ea-ch ofthese plates is composed of alternating adjacent strips and 111 of ametal capable of being magnetized and Aof a non-magnetic material sothat the lines 112 of flux extend around (FIG. 8) the non-magneticmaterial rather than being shorted through the metal. This provides 4fora more even build-up of metal particles throughout the entire surfacearea of the adjacent liner 60.

Another embodiment of the invention is shown in FIG. 9 wherein thehousing 20a and its components are identical to those described above.However, a rectangular duct 120 coextensive with the top wall 23a of thehousing is mounted on this top wall with the inlet 121 disposedimmediately above the front edge 26a of the housing. A screen or othergrill work 122 may be provided on the inlet, and the outlet 123 isconnected through a cartridge type filter 125 to a vacuum pump 126. Thuswhen the apparatus is in use, the pump 126 draws air laden withnon-metallic dust particles from the space surrounding the grindingoperation, through the duct 120 and into the filter 125 wherein the dustparticles are collected. This iilter can be removed and cleaned orreplaced from time to time. Because the non-metallic particles producedduring the grinding operation are relatively light they float in thearea surrounding the grinding operation, and a large portion thereof aredrawn into the duct 120 by the air flow created by the vacuum pump.

Accordingly, the invention has provided a magnetic dirt collector forcollecting the particles created during the grinding operation. A majorportion of these particles is caused to adhere on the inside surfaces ofthe housing by the fields of magnetic flux which are created by theelectromagnets therein. The instantaneous polarity reversing facilitatesquick emptying of the particles from the housing which can be adjustedin substantially a universal manner to accommodate workpieces ofdifferent sizes and dimension.

The invention thus provides a noiseless, inexpensive, compact, andeicient apparatus for collecting the dirt particles produced duringgrinding, without interference with the air conditioning system. While aspecific structural arrangement has been shown, it is within the scopeof the invention to create the magnetic field by other types andarrangements of electromagnets, permanent magnets, or combinationsthereof, and the shape of the housing is in no way a limitation on theinvention. Likewise, the posts and bars may be eliminated withoutdeparting from the scope of the invention, and other types of baiiiesand magnetic fiux distributing members may be utilized. It is alsopossible to mount the housing 2lifor movement with a grinding wheel in amachine wherein the workpiece reciprocates rather than vice versa, asshown.

While the forms of apparatus herein described constitute preferredembodiments of the invention, it is to be understood that the inventionis not limited to these precise forms of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. A magnetic dirt collector for accumulating the metal particles from astream of particles produced as a grinding wheel grinds a metalworkpiece, said collector comprising a housing adapted to be positionedfor cooperation with a grinding machine, means defining an opening losaid housing for receiving the stream of dirt from the grinding machine,and magnetic means associated with said housing 'for creating a magneticfield to attract and deposit metallic particles on the inside sur-facesof said housing.

2. A magnetic dirt collector as defined in claim 1 comprising mountingmeans for said housing adapted to permit adjustment in the position ofsaid housing to substantially any direction to enable the stream ofparti-cles to pass into said opening.

3. A magnetic dirt collector as defined in claim 1 wherein said magneticmeans includes a plurality of electromagnets adapted to create amagnetic field on the inside surfaces of said housing.

4. A magnetic dirt collector as defined in claim 3 wherein said housingincludes an outer wall adapted to support a plurality of spacedelectromagnetic devices, each of said devices including a flat plate onthe inside thereof closely spaced from said plates on the adjacentelectromagnetic devices, and an inner liner of non-magnetic materialsupported adjacent said plates to define a chamber adapted to receivethe stream 'of particles through said opening.

5. A magnetic dirt collector as defned in claim 4 wherein each of saidplates has a finger on the inner portion thereof which extends inwardly,said fingers being spaced from one another and defining a rear walladapted to have a magnetic field created therein.

-6. A magnetic dirt collector as defined in claim 4 wherein a pluralityof projections are provided on the inside surface of said liner to alterthe magnetic field.

7. A magnetic dirt collector as defined in claim 4 wherein a pluralityof baiiie means are provided on the inside surface of said housing fordefiecting the stream of particles against the surfaces of said housing.

-8. A magnetic dirt collector as defined in claim 7 wherein said batilemeans are metal bars connected to said electromagnetic device tomagnetize said bars and permit accumulation of metal particles thereon.

9. A magnetic dirt collector as defined in claim 3` comprising meansadapted to connect a source of direct current to said electromagneticdevices, and switch means for momentarily reversing the direction offiow of the direct current to repel the metal particles from saidhousing to `facilitate removal of the particles from said housing.

10. A magnetic dirt collector as defined in claim 1 wherein a vacuumdevice is associated with said housing for drawing the air surroundingsaid opening of said housing thereinto thus removing the non-magneticparticles.

11. A magnetic dirt collector as defined in claim 10 wherein said vacuumdevice includes filter means for removing the solid particles in the airdrawn into said vacuum device.

12. A magnetic dirt collector as defined in claim 4 wherein said platesare composed of adjacent strips of magnetizable and non-magnetizablematerials so that the References Cited UNITED STATES PATENTS 3/ 1931Hallam 51-270 4/1921 Graham 51-270 JAMES L. JONES, JR., Primary ExaminerU.S. Cl. X.R. 5l-273

